1. Field of the Invention
The present invention relates generally to improvements to techniques used to splice optical fiber, and more particularly to advantageous aspects of systems and methods for low-loss splicing of optical fibers having a high concentration of fluorine to other types of optical fiber.
2. Description of the Prior Art
A new class of optical fibers has recently been developed known as dispersion-compensating fiber (DCF), which has a steeply sloped, negative dispersion characteristic. One use for DCF is to optimize the dispersion characteristics of already existing optical fiber links fabricated from standard single-mode fibers (SSMF) for operation at a different wavelength. This technique is disclosed in U.S. patent application Ser. No. 09/596,454, filed on Jun. 19, 2000, assigned to the assignee of the present application, the drawings and disclosure of which are hereby incorporated by reference in their entirety.
An important parameter for DCF is the excess loss that results when DCF is spliced to SSMF. To obtain a highly negative dispersion, DCF uses a small core with a high refractive index, having a mode-field diameter of approximately 5.0 xcexcm at 1550 nm, compared with the approximately 10.5 xcexcm mode-field diameter of SSMF at 1550 nm. The difference in core diameters results in significant signal loss when a fusion splicing technique is used to connect DCF to SSMF. It is possible to reduce the amount of signal loss by choosing splicing parameters that allow the core of the DCF to diffuse, thereby causing the mode-field diameter of the DCF core to taper outwards, resulting in a funneling effect. However, the high concentration of fluorine dopant in typical DCFs limits the application of this technique, because the amount and duration of the heat required to produce the funneling effect may result in an undesirable diffusion of the fluorine dopant.
There is thus a need for improved techniques for splicing DCF to SSMF that reduces splice loss below current limits.
The above-described issues and others are addressed by the present invention, aspects of which provide methods and systems for splicing together first and second optical fibers. One aspect of the invention provides a thermal treatment station, comprising a chassis, a fiber holding block for holding a pair of optical fibers that have been spliced together at a splice point, the fiber holding block including a cutaway portion exposing the splice point, and a torch. The fiber holding block and the torch are preferably mounted to the chassis such that the positions of the splice point and the torch can be adjusted with respect to each other so that the splice point lies in the flame. A further aspect of the invention provides a method for splicing together two optical fibers in which the optical fibers are first spliced together using a fusion splicer and then thermally treated by positioning the splice point in a flame while monitoring splice loss.
Additional features and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings.